What is Cushing’s syndrome?

Cushing’s syndrome occurs in dogs with high levels of the hormone cortisol. Cortisol normally gets released into the bloodstream at times of stress to prepare the body for a fight or flight response. In dogs with Cushing’s syndrome, the level of cortisol released is excessive and, if left untreated, becomes incapacitating.

How is cortisol produced?

Two small glands situated near the kidneys - the adrenal glands - produce cortisol.

The production and release of cortisol from the adrenal glands is controlled by the hormone ACTH. A pea-sized gland at the base of the brain called the pituitary gland is responsible for the production of ACTH.

Common forms of Cushing’s syndrome

There are two common forms of Cushing’s syndrome:

Pituitary-dependent Cushing’s syndrome

This is the most common form of the disease. It occurs as a result of a slow growing tumour in the pituitary gland. This tumour produces large amounts of the hormone ACTH.


Adrenal-dependent Cushing’s syndrome

This form of the disease occurs when a tumour producing large amounts of cortisol develops in one, and sometimes both, of the adrenal glands.

These tumours are responsible for the excessive release of cortisol into a dog’s bloodstream. Over time, the clinical signs of Cushing’s syndrome will become more and more noticeable.

How do I know if my dog has Cushing’s syndrome?

Cushing’s syndrome is usually seen in older dogs. Small breed dogs are more likely to develop the disease. Signs of the disease are very similar to those associated with normal ageing, which can make it difficult to diagnose.

The most common signs to look for include:

Your dog may not necessarily display all of these signs. If you become concerned about your dog’s health and welfare, you should consult your veterinary surgeon immediately.

How will my veterinary surgeon diagnose the disease?

If your veterinary surgeon suspects Cushing’s syndrome in your dog, he/she will perform blood tests to confirm the diagnosis. However, since the disease can be difficult to diagnose, several tests may need to be performed. Cortisol levels found in the blood of both healthy dogs and dogs with Cushing’s syndrome fluctuate greatly during the day. Therefore, cortisol measurement alone does not provide accurate diagnosis or confirmation of the disease.

Your veterinary surgeon will want to determine how much excess cortisol your dog’s adrenal glands actually produce. This can be done with an ACTH stimulation test.  Alternatively, your veterinary surgeon may decide to perform a low-dose dexamethasone suppression test. This test assesses how easily the production of cortisol by the adrenal glands is controlled. In some cases it may be necessary to perform both tests.

You will normally need to leave your dog with your veterinary surgeon for a few hours or for the day so that these tests can be carried out.